Method of treating a material to achieve sufficient hydrophilicity for making hydrophilic articles

ABSTRACT

An exemplary method of treating a material such as carbon or graphite to render at least some surfaces of the material hydrophilic includes coating at least a portion of the at least some surfaces with an oxygenated element and controlling a rate of a breakdown of the oxygenated element to leave a corresponding elemental oxide on the surfaces. In one example, the material is treated before being incorporated into an article comprising the material. Another example method includes treating an article comprising the material. Disclosed examples include precipitation or decomposition as the breakdown of the oxygenated element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.11/320,517, which was filed on Dec. 28, 2005, and a continuation-in-partof U.S. application Ser. No. 11/567,480, which was filed on Dec. 6,2006.

BACKGROUND

A variety of situations require hydrophilic articles. One example iswithin the fuel cell art. Many fuel cell arrangements include watertransport plates for controlling water, air and fuel flow within a fuelcell assembly in a known manner. Traditionally, water transport plateshave included porous, hydrophilic flow fields that include flow channelsfor directing fluid in a desired manner. Many such flow fields comprisegraphite, a resin and a wettability component. For example, it is knownto treat porous graphite plates with a metal oxide post-treatment toimpart wettability to the plate. It is also known to add a metal oxideas one of the components for making a water transport plate. Anotherexample includes adding hydrophilic carbon black. In many of thoseinstances, the wettability component is added as a separate component ina mixture containing resin such that the resin binds the wettabilitycomponent in place. There is no effect on the graphite, itself, usingthe traditional approach.

U.S. Pat. No. 5,942,347 shows one example technique where a porousbi-polar separator plate has at least one electronically conductivematerial, at least one resin and at least one hydrophilic agent. Each ofthese components is substantially uniformly distributed throughout theseparator plate of that document. The hydrophilic agent in that documentis selected from material such as oxides of Ti, Al, Si and mixtures ofthem. There are at least two difficulties with this approach. First, itis very difficult to uniformly distribute materials as suggested in thatpatent. Secondly, because the oxides are dielectric, using hydrophilicor wetting agents of the type described there can increase theelectrical resistance of such a separator plate, which is undesirable.Therefore, it is difficult to achieve uniform distribution as suggestedin that document without increasing electrical resistance.

Such wettability treatments or additives have been required because thegraphite is generally hydrophobic. Without the wettability agent ortreatment, traditional graphite based water transport plates arehydrophobic and not suitable for their intended use. Graphite particlescomprise carbon atoms arranged in a manner that typically provides arelatively low surface energy such that the graphite particles areessentially hydrophobic. Carbon atoms within a graphite crystal arearranged in a plurality of generally parallel planes. The bonds betweenthe carbon atoms within the planes are very strong. Graphite particlesurfaces that are aligned with such planes (i.e., basal plane surfaces)have a relatively low surface energy.

It is desirable to provide an improved process for making hydrophilicarticles such as water transport plates. For example, it would be usefulto make the fabrication process less complicated and to reduce costs bytaking a different approach that does not include the traditionalwettability additives or wettability enhancing agents. This inventionaddresses that need.

SUMMARY

An exemplary method of treating a material to render at least somesurfaces of the material hydrophilic includes coating at least a portionof the at least some surfaces with an oxygenated element and controllinga rate of a breakdown of the oxygenated element to leave a correspondingelemental oxide on the surfaces.

In one example, the material is treated before being incorporated intoan article comprising the material. Another example method includestreating an article comprising the material. Disclosed examples includeprecipitation or decomposition as the breakdown of the oxygenatedelement. Disclosed examples include carbon and graphite as the materialthat is treated.

The various features and advantages of the disclosed examples willbecome apparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an example water transport plateassembly including a hydrophilic structure designed according to anembodiment of this invention.

FIG. 2A schematically shows a feature of a crystal structure of anexample graphite particle.

FIG. 2B schematically shows another view of the crystal structure ofFIG. 2A.

FIG. 3 illustrates elemental oxide deposition results obtained in oneexample embodiment of this invention.

FIG. 4 illustrates elemental oxide deposition results obtained in anexample embodiment according to the prior art.

FIG. 5 schematically illustrates an example manufacturing process.

FIG. 6 schematically illustrates a portion of an example article madefrom the example process of FIG. 5.

DETAILED DESCRIPTION

Disclosed example methods of treating a normally hydrophobic materialsuch as carbon or graphite renders at least some surfaces of thematerial hydrophilic, which is useful for establishing a hydrophilicityor wettability for an article including that material.

One example use of such an article is in a fuel cell. FIG. 1 shows aschematic, cross-sectional representation of an electrochemical cellsuch as a fuel cell 10 for generating electrical energy from processoxidant and reducing fluid reactant streams. The example fuel cell 10has a porous carbon body comprising a first or anode water transportplate 12 and a second or cathode water transport plate 14. The anode andcathode water transport plates 12, 14 are at opposed sides of themembrane electrode assembly 16, which includes a membrane electrodeassembly 16 that consists of an electrolyte such as a proton exchangemembrane 18, an anode catalyst 20 and a cathode catalyst 22. Theillustration also shows bi-layer gas diffusion layers 24, 26 and 28, 30.In some examples only the layers 24 and 28 would be used as known.

The anode water transport plate 12 includes a plurality of fuel flowchannels 32 that are in fluid communication with each other and with afuel inlet 34 that receives the reducing fluid so that the fuel inlet 34and flow channels 32 cooperate to pass the reducing fluid fuel throughthe fuel cell 10 in fluid communication with the anode catalyst 20.Similarly, the cathode water transport plate 14 includes a plurality ofoxidant flow channels 36 that are in fluid communication with each otherand with an oxidant inlet 38 that receives the process oxidant so thatthe oxidant inlet 38 and oxidant flow channels 36 cooperate to pass theprocess oxidant through the fuel cell 12 in fluid communication with thecathode catalyst 22.

Water transport plates serve many functions in a fuel cell. Namely, theydeliver reactants to membrane electrode assembly catalysts; transportproduct water away from the cathode to prevent flooding; humidify theanode and/or cathode reactant streams; provide a wet seal barrierbetween reactants and/or coolants; and act as an electrical conductor tocarry electrical current to the collectors. Accordingly, the porestructure must be designed to provide the desired capillary action andassure sufficient hydrophilicity to facilitate water movement. Somearrangements include porous and non-porous sections, but the poroussections must have sufficient hydrophilicity.

As mentioned above, the traditional approach for making water transportplates renders them hydrophobic unless a wettability agent has beenincorporated as a raw material ingredient in the manufacturing processor in a post-treatment process. The graphite as used in many previouswater transport plates is hydrophobic, or insufficiently hydrophilic,which has made it necessary to include a separate wettability agent.

There are other articles for which wettability and water transportproperties are required. For example, some fuel cell applicationsutilize evaporative cooling. Some portions of such fuel cellarrangements require sufficient wettability to accomplish the desiredwater transport from the liquid zone to the evaporative zone. Anotherexample article within a fuel cell that may need to be wettable orhydrophilic is the gas diffusion layer such as the layers 24 and 28. Thecarbon used for many previous gas diffusion layers is hydrophobic, orinsufficiently hydrophilic, which has required adding a separatewettability agent to make a hydrophilic gas diffusion layer.

The hydrophilicity of an object is a surface property characteristicthat describes wetting behavior, which is the interaction of a liquidwith a solid. For example, wetting is observed in the spreading of aliquid over a surface, in penetration of a liquid into a porous medium,or in displacement of one liquid by another. Wetting refers to themacroscopic manifestation of molecular interaction between liquids andsolids in direct contact at the interface between them. Increasedwettability ensures uniform spreading of a liquid over a solid surfaceor better penetration of a liquid through a porous medium, for example.

Wettability is typically determined by the balance between adhesiveforces between the liquid and solid and cohesive forces in the liquid.Adhesive forces cause a liquid drop to spread. Cohesive forces cause theliquid drop to remain balled up.

The contact angle between the liquid and the solid is determined bycompetition between the adhesive and cohesive forces. When a surface iswettable or hydrophilic, the contact angle with water is less than 90°.Hydrophilic materials possess high surface energy values and the abilityto form “hydrogen bonds” with water. By contrast, hydrophobic ornon-wettable materials have little or no tendency to absorb water sothat water tends to “bead up” on the surface in the form of discretedroplets. The contact angle with water for hydrophobic surfaces isgreater than 90°. Hydrophobic materials possess low surface energyvalues and lack active groups in the surface chemistry for forming“hydrogen bonds” with water.

We consider graphite as one example type of carbon for discussionpurposes. To understand the wettability of graphite, it is useful toconsider its structure. Graphite is composed of infinite layers ofcarbon atoms arranged in the form of hexagons (or rings) lying inplanes. The layers are stacked parallel to each other. Each carbon atomwithin the plane is covalently bonded (e.g., is tightly bound) to threeother carbon atoms. The atoms in alternative planes align with eachother and are loosely bonded by van der Waals forces.

FIGS. 2A and 2B schematically illustrate an example crystallinestructure of a portion of an example graphite particle 52. A pluralityof carbon atoms 54 are arranged into a plurality of hexagons that liewithin a plurality of planes. The illustration includes a first plane56, a second plane 58 and a third plane 60. The covalent bonds betweenthe carbon atoms 54 within the planes are very strong. The bonds betweencarbon atoms of one plane and carbon atoms of another plane, on theother hand, are much weaker.

Surface areas on the graphite particle aligned with the planes (e.g.,generally parallel to the first plane 56) are referred to as a basalplane surface such as that schematically shown at 62. Ideal basal planesurfaces, which means defect free and contamination free, arehomogenous, generally “smooth” and consist only of carbon atoms. Eachgraphite particle will have at least one basal plane surface 62 and atleast one prismatic surface 64. The usual shape of graphite powder isplatelets or flakes with basal sites that have a low surface energy.Flake graphite has a majority of the overall graphite particle surfacearea within a basal plane surface.

The strong bonds between the carbon atoms 54 within the basal planesyields a relatively low basal plane surface energy and a resultinghydrophobic surface.

The relatively weaker bonds (from van der Waals forces) between carbonatoms in different planes provides a higher surface energy alongprismatic surfaces 64. The prismatic surfaces are distinguishable frombasal plane surfaces 62 because the prismatic surfaces are arranged atleast partially oblique to the orientation of the planes 56, 58 and 60,for example. It is sufficient for purposes of discussion to understandthat normally there is a different surface energy on the basal planesurfaces 62 compared to the surface energy on the prismatic surfaces 64.

The relatively weak links between carbon atoms along the prismaticsurfaces 64 and the heterogeneous nature of the prismatic surfaces(e.g., prismatic surfaces typically include various, mostlyoxygen-containing functional surface groups along with the carbon atoms)gives the prismatic surfaces 64 a higher surface energy. The prismaticsurface 64 can be considered a polar surface. As a result, the prismaticsurfaces 64 are hydrophilic and can form strong hydrogen bonds withwater molecules.

The hydrophobic and hydrophilic character of the graphite surfaces on agraphite particle can be characterized by a wettability ratio, which canbe expressed by the following relation:${{Wettability}\quad{Ratio}} = \frac{{The}\quad{hydrophilic}\quad{surface}\quad{area}}{{The}\quad{total}\quad{surface}\quad{area}}$According to this definition, the wettability ratio can varysignificantly: from almost one (for theoretical, ideal, perfectly sphereshaped graphite which has all surface area formed by the prismaticsurfaces) to a very low value for graphite with predominantly basalplane surface. The higher the wettability ratio of graphite, the betterits wettability.

In one example, the wettability ratio equals the ratio of prismaticsurface area to the total surface area.

Prismatic (e.g., hydrophilic) surface area and total surface area can bedetermined experimentally. The hydrophilic (and hydrophobic) characterof graphite surfaces can be determined by absorption calorimetry, or byflow microcalorimetry. The total surface area can be determined by theBrunauer, Emmett and Teller (BET) method. A very exact method useful inbreaking down the total surface area of graphite into fractions of basalplane surfaces and prismatic surfaces is krypton gas absorption.

The relative hydrophilicity between differing graphites can bedetermined using known techniques such as the Washburn method (orCapillary Rise Method), which is well known from published literature.This technique allows for obtaining the values of contact angles, whichindicates in a relative manner whether a surface is hydrophilic (i.e.,wettable) or hydrophobic.

One example embodiment of this invention includes the realization thatincreasing the amount of prismatic surface area within graphite used forforming a hydrophilic article establishes sufficient wettability for thearticle to meet the hydrophilicity needs of a particular situation. Ithas been found, for example, that using sufficiently wettable graphiteparticles as at least a portion of the graphite used to make the articlecan establish a sufficient wettability to meet the needs for many fuelcell applications.

One example includes selecting graphite particles having a wettabilityratio, which is the ratio of the hydrophilic surface area to the totalsurface area, within a range sufficient to make the resulting articlehydrophilic. In other words, selecting enough of the graphite particlesto have a particular physical characteristic results in enough wettable(e.g., prismatic) surface area compared to the hydrophobic (e.g., basalplane) surface area to render the resulting article hydrophilic. Byappropriately selecting graphite particles, the wettability of ahydrophilic structure can be established purely by the graphiteparticles.

In one example, the selected graphite particles have a wettability ratiothat is more than about 0.10. This is achieved in one example, byselecting graphite particles that have at least about 10% prismaticsurface area with a remaining percentage basal surface area.

One example includes selecting graphite particles having a wettabilityratio greater than 0.18. In this example, provided that there are enoughgraphite particles having at least about 18% wettable (e.g., prismatic)surface area, sufficient wettability can be obtained for many fuel cellwater transport plate applications. One example includes selectinggraphite particles that are generally spheroidal. Such particles havemore prismatic surface area than flake graphite. One particular exampleincludes spheroidal graphite particles as the majority of the graphite.Another example includes spheroidal graphite particles, exclusively.Strategically controlling the amount and type of graphite particles thatare included will provide wettability in an amount sufficient to meetthe needs of a given situation.

A variety of commercially available spheroidal graphite materials areknown. Prior to this invention, however, no one has considered thewettability aspects of such particles. Instead, they have been alwaysused with a wettability agent. U.S. Pat. No. 6,746,982, for example,mentions the use of Timcal KS75 and KS150 graphite, both of which arespheroidal. That patent teaches adding a wettability treatment. U.S.Pat. No. 6,926,995 suggests using natural or synthetic graphite for aporous separator plate and teaches that the graphite is not subject toany particular limitation. That patent is another example of thetraditional thinking that adding a hydrophilic agent is necessary toachieve wettability.

Wettability agents typically have been introduced along with resin andgraphite particles. In those instances, wettability agents have beensecured to the structure or made part of the structure by the bindingaction of the resin. In other words, the wettability agents did notdirectly impact the graphite because they were present within thecomposite and typically held in position by the resin.

As mentioned above, one example implementation of this inventionincludes using generally spheroidal graphite particles because of theirrelatively higher percentage of prismatic surface area compared to flakegraphite, for example. Another example includes using expanded graphiteparticles to achieve the desired wettability ratio. Expanded graphiteparticles are known. Expanded graphite particles have larger distancesbetween the parallel plane of carbon atoms, which provides an increasedprismatic surface area compared to non-expanded graphite particles. Oneembodiment of this invention includes using at least some expandedgraphite particles within the graphite to provide hydrophilicity to aresulting article.

Another example includes pretreated graphite particles that haveincreased wettable surface area compared to pure or untreated graphite.In one example, the basal plane surface of the pretreated graphiteparticles have some wettability along with the wettability of theprismatic surfaces such that a higher percentage of hydrophilic surfacearea exists compared to pure or untreated graphite.

One example includes treating the basal surfaces of the graphite tocreate defects on the basal planes using a plasma, laser or othersurface treatment. Defects on the basal planes will interrupt orinterfere with the otherwise present strong covalent bonds between thecarbon atoms, which will increase the surface energy and the wettabilityof a basal surface. In such an example, at least some of the basal planesurface area can be considered as part of the hydrophilic surface areaalong with the already hydrophilic prismatic surface area.

Another example includes using a deposition process to effectivelymodify a surface of an otherwise hydrophobic material such as the basalsurface of graphite particles. Examples include coating at least aportion of at least some surfaces of the hydrophobic material with anoxygenated element and controlling a rate of a breakdown of theoxygenated element to leave a corresponding elemental oxide on thesurfaces. One example method includes decomposition as at least part ofthe breakdown of the oxygenated element. Another example method includesprecipitation as at least part of the breakdown of the oxygenatedelement.

In one example, pure graphite is mixed with an organic titanate in anethanol solution. One example includes using Tyzor® (tetra n-butyltitanate (TnBT)), which is available from Dupont. In one example, theamount of titania (TiO₂) constitutes 0.4-0.5 mass % of the graphite.

Organic butyl titanate solution is mixed with a solvent (denaturedethanol) and graphite. The butyl titanate and solvent undergo ametathetical ligand exchange (room temperature decomposition) to formtitanium tetraethanolate, butanol, and ethanol. The alcohols are thendecanted, and the resulting slurry is then heated at 350° C. tocompletely decompose the remaining organic components, resulting in TiO₂being deposited on the basal plane surface of the graphite.

When such an organic butyl titanate solution is heated, ethanol will beevaporated and butyl titanate will be decomposed into TiO₂ by thefollowing reaction:Ti(OCH₄H₉)₄+4(C₂H₅OH)==>Ti(OC₂H₅)₄+4(C₄H₉OH)==>Ti(OC₂H₅)₄+heat(350°C.)==>T_(i)O₂

The result is the presence of TiO₂ on surfaces of the graphiteparticles. The deposited TiO₂ on the graphite particles renders thosesurfaces at least partially wettable. We believe the presence ofunsaturated Ti atoms, which can be easily combined with oxygen atoms inwater to form Ti—OH layers, renders such a surface hydrophilic orwettable. On some surfaces, 2-3 layers of physically absorbed water arefurther formed.

From one perspective, pretreating graphite as described above increasesthe surface energy of the surfaces where the TiO₂ is deposited. In someexample embodiments of this invention, the pretreated graphite particlesinclude basal plane surfaces with a higher surface energy compared tountreated graphite such that the pretreated basal surfaces arehydrophilic.

In one particular example, 25 g of graphite powder KS5-75TT (d90=70micron) was added to 40 ml of an ethyl solution and mixed atapproximately 1000 rpm in a 3-propeller Barnant mixer. A selected amountof Tyzor® (0.5326 g of Tyzor® TnBT 23.5 mass % TiO₂ in 25 g of graphite)was dissolved into 50 ml of the ethanol solution and added to thegraphite slurry. The mixture was stirred for fifteen minutes and placedin a large glass dish. That was then placed into a nitrogen purged ovenin which the temperature was slowly ramped to 200° C. at a rate of 10°C. per minute. The graphite resided isothermally at 200° C. for 20minutes and then the temperature was ramped to 350° C. at a rate of 10°C. per minute. In this example, the temperature of 350° C. wasmaintained for 10 minutes before turning off the oven and letting itcool down slowly to room temperature.

In one example, deposited TiO₂ was examined qualitatively using EnergyDispersive Spectroscopy (EDS) and quantitatively by Inductively CoupledArgon Plasma (ICP). The EDS results confirmed the presence of TiO₂ onthe graphite and the ICP results demonstrated that the amount of TiO₂was close to 0.5 mass % of graphite. The surface morphology of thedeposited TiO₂ was characterized using Scanning Electron Microscopy(SEM). White deposits of TiO₂ were seen on the basal plane surface ofgraphite particles and their estimated dimensions were in a nanometerrange.

In the just-described example, the graphite particles were treated tohave TiO₂ deposited on at least one basal surface of the graphiteparticles before they were used for making a hydrophilic article, suchas a plate for use in a fuel cell. One example article into which suchtreated graphite particles are incorporated comprises a water transportplate for use in a fuel cell.

In another example, at least one other oxygenated element andcorresponding elemental oxide is used for treating the graphiteparticles using the same controlled breakdown process (e.g.,decomposition). One example includes using a zirconate and depositingZrO₂ on basal plane surfaces of at least some of the treated particles.Another example includes SiO₂ based upon a silicate. Other examplesinclude oxides based on at least one of a stannate, an aluminate or atantalate.

Any of the above oxygenated elements used for forming the oxide to treatthe graphite particle basal surfaces can be processed in the mannerdescribed above for the example that results in TiO₂ deposits. Any oneof the mentioned oxygenated elements could be used or a combination ofthem could be used to provide the oxides.

In one example, the article is made before the material (e.g., graphiteor carbon) is treated. In one example, an article is first formed andthen subsequently treated to increase the surface energy of surfaces ongraphite particles by depositing TiO₂ on the particles within thearticle. Wettability is also increased because the TiO₂ is deposited onany existing binder such as a resin binder. Example articles treated inthis manner include water transport plates and gas diffusion layers.

In one particular example, 1.0654 g of 0.5 mass % organic titanate (inthe form known as Tyzor® TnBt) was weighed into a 100 mL beaker with 50g of denatured ethanol (JT Baker, PSIII-Product No. 9287). A 2×2 inchsample of a porous graphite plate was placed into the solution andsubjected to vacuum impregnation. The sample was subsequently dried atroom temperature for 30 minutes. The sample was then backfilled byplacement into a solution of 4.7 mass % of dionized water (36.03 g) in764.5 g denatured ethanol for 30 minutes at room temperature. The samplewas then placed into an oven at 115° C. (240° F.).

The resulting sample had an increased hydrophilicity compared to thesample before the example treatment process. The resulting deposition ofTiO₂ on at least some basal surfaces of graphite particles increase thehydrophilicity of those particles, which renders the articlehydrophilic. The solvent (denatured ethanol) has the effect of slowingdown a rate of precipitation (i.e., breakdown) of titania from thetitanate. Without the solvent, mixing moisture from air and a titanatesuch as Tyzor® results in an essentially instantaneous reactionresulting in precipitated titania (TiO₂) from the titanate. Using asolvent in one example allows for controlling the rate of precipitation.This allows for an article to be coated with the titanate beforeprecipitation. In one example, this results in a much higherhydrophilicity because it is believed that the attachment of theoxygenated element to the graphite prior to the breakdown (i.e.,precipitation) allows a far greater incidence of the elemental oxide(e.g., titania) deposited on the graphite.

FIG. 3 shows the results obtained in one example. The elemental oxidedeposits are shown at 70. The incidence of such deposits is much greaterin FIG. 3 compared to the deposits 70′ as shown in FIG. 4, which isconsistent with the results obtained using a previous approach wherethere is no control over the breakdown of titanate so that titania isprecipitated before introducing the graphite article. In other words,the example approaches that include coating graphite particle surfaceswith an oxygenated element and controlling a breakdown rate to leave thecorresponding elemental oxide on the surfaces provide more elementaloxide deposition and higher hydrophilicity. Another feature of theexample results shown in FIG. 3 is that the elemental oxide deposits 70are essentially sphere-shaped, which is indicative of a completedchemical reaction. By contrast, the deposits 70′ in FIG. 4 are randomlyshaped, which is the type of result obtained when titania is allowed toform in a mixture before an article comprising graphite is introducedinto the mixture.

One advantage to an approach for treating an article comprising graphitecompared to pretreating the graphite particles themselves is that thearticle treatment approach can provide the intended hydrophilicity usinglower temperatures, which requires less energy. Another advantage isthat the associated cost, complexity and required time are reducedcompared to pretreating graphite particles. Another advantage is thatall constituents within the article will be rendered at least somewhathydrophilic because the elemental oxide (e.g., TiO₂) is depositedeverywhere on the article.

FIG. 5 schematically shows one example technique of making a hydrophilicarticle designed according to an embodiment of this invention. Agraphite supply 100 includes a plurality of graphite particles having awettability ratio of a hydrophilic surface area to a total surface areathat is within a range sufficient to make the article hydrophilic asdiscussed above. In one example, the included plurality of graphiteparticles are generally spheroidal. In another example, the plurality ofincluded graphite particles comprise expanded graphite. In still anotherexample, the included plurality of graphite particles comprisepretreated graphite having an altered basal plane surface that ishydrophilic. One example comprises a basal plane surface includingelemental oxide (e.g., TiO₂) deposits. Another example in which anarticle is formed prior to the treatment of the graphite includes anelemental oxide on basal plane surfaces of graphite particles in whichthe elemental oxide results from using at least one of a titanate,zirconate, stannate, aluminate, silicate or tantalate.

The graphite from the supply 100 is mixed with a resin 102 and a mold104 is used to form a resulting article 106. FIG. 6 schematically showsa portion of the resulting article 106. In the example of FIG. 6, thearticle is porous and includes some graphite particles that aretraditional flake graphite shown at 110 and other graphite particlesthat have a wettability ratio that is within a range sufficient to makethe article hydrophilic. These graphite particles are shown at 112. Theresin from the supply 102, which binds together graphite particles, isschematically shown at 114. Voids or passages 116 exist between graphiteparticles, which renders the resulting article porous. In one example,the wettable surface of the graphite particles 112 is adjacent to orwithin the voids or passages 116.

Depending on the performance characteristics required for the resultingarticle and the type of graphite selected for forming the article,different wettability ratios will provide the intended results fordifferent operating conditions. Given this description, those skilled inthe art will be able to select appropriate wettability ratios andpercentages of appropriate graphite particles to provide a hydrophilicarticle that meets their particular needs without requiring awettability agent or additive in the graphite-resin mixture.

Graphite is used in the examples described above as one example type ofcarbon that can be treated in accordance with the disclosed methods.Another example includes carbon as the material that is treated torender at least some surfaces of the carbon hydrophilic. Untreatedcarbon is otherwise a generally hydrophobic material. In one particularexample, a gas diffusion layer comprising carbon is treated by coatingat least a portion of at least some surfaces of the carbon with anoxygenated element. Controlling a rate of a breakdown of the oxygenatedelement (e.g., by including one of the example solvents mentioned abovein the mixture) allows for leaving deposits of the correspondingelemental oxide on the surfaces of the carbon. This renders the treatedcarbon hydrophilic enough to provide the desired wettability orhydrophilicity of the article (e.g., the gas diffusion layer) for itsintended use in a fuel cell, for example.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this invention. The scope of legal protection given tothis invention can only be determined by studying the following claims.

1. A method of treating a material to render at least some surfaces ofthe material hydrophilic, comprising coating at least a portion of theat least some surfaces with an oxygenated element; and controlling arate of a breakdown of the oxygenated element to leave a correspondingelemental oxide on the surfaces.
 2. The method of claim 1, wherein thebreakdown comprises decomposition.
 3. The method of claim 1, wherein thebreakdown comprises precipitation.
 4. The method of claim 1, comprisingmixing the oxygenated element with a solvent to control the rate ofbreakdown.
 5. The method of claim 4, comprising using the solvent toslow a rate of at least one of decomposition or precipitation.
 6. Themethod of claim 4, comprising combining the oxygenated element and thesolvent to establish a solution; placing an article comprising thematerial into the solution; and impregnating the article with at leastsome of the solution.
 7. The method of claim 6, comprising subjectingthe article in the solution to vacuum impregnation.
 8. The method ofclaim 6, comprising subsequently drying the article; subsequentlyplacing the dried article into a second solution comprising water and asolvent; and subsequently heating the article.
 9. The method of claim 8,wherein the second solution comprises deionized water and denaturedethanol.
 10. The method of claim 8, comprising heating the article at atemperature greater than 100° C.
 11. The method of claim 4, comprisingheating a mixture of the oxygenated element, the material and thesolvent to a first temperature; subsequently heating the heated mixtureto a second, higher temperature; and subsequently allowing the mixtureto cool to room temperature.
 12. The method of claim 11, comprisingincreasing a temperature of a device used to heat the mixture at acontrolled rate to reach the first temperature; and increasing thetemperature from the first temperature to the second, higher temperatureat approximately the same controlled rate.
 13. The method of claim 11,comprising maintaining the heated mixture at the first temperature for afirst amount of time; and maintaining the heated mixture at the secondtemperature for a second amount of time that is approximately half aslong as the first amount of time.
 14. The method of claim 11, comprisingheating the mixture at a temperature greater than 300° C.
 15. The methodof claim 4, wherein the solvent comprises at least one of an ethylsolution, an ethanol solution or a denatured ethanol.
 16. The method ofclaim 1, comprising treating the material by performing the coating andthe controlling prior to incorporating the material into an article. 17.The method of claim 1, comprising forming an article comprising thematerial; and subsequently treating the material by performing thecoating and the controlling.
 18. The method of claim 1, wherein the atleast some surfaces comprise basal surfaces of the material and themethod comprises increasing a surface energy of the basal surfaces. 19.The method of claim 1, wherein the oxygenated element comprises ametallic element.
 20. The method of claim 19, wherein the metallicelement comprises at least one of a titanate; a zirconate; a stannate;an aluminate; or a tantalite.
 21. The method of claim 1, wherein theoxygenated element comprises a non-metallic element.
 22. The method ofclaim 21, wherein the oxygenated element comprises a silicate.
 23. Themethod of claim 1, wherein the material comprises carbon.
 24. The methodof claim 1, wherein the material comprises graphite.